As a cutting method of a semiconductor substrate and the like, Stealth Dicing (registered trademark) has been known (JP-A 2009-135342). This cutting method is a technique in which laser light with a wavelength passing through a semiconductor substrate (for example, silicon (Si)) is collected inside the semiconductor substrate to form a reformed region (flaw region) inside the semiconductor substrate, and then an external stress such as a tape expansion is applied to cause a crack in the semiconductor substrate starting from the reformed region and cut the semiconductor substrate.
This cutting method enables the reformed region to be locally and selectively formed inside the semiconductor substrate without damaging a principal surface of the semiconductor substrate, and therefore it is possible to reduce occurrence of defects such as chipping and the like on the principal surface of the semiconductor substrate that is a problem in general blade dicing. In addition, there are fewer problems such as dust occurrence unlike machining. Therefore, in recent years, the above-described cutting method becomes to be widely used not only in cutting the semiconductor substrate but also in cutting a glass plate.